Shielding against radiation from the irradiated fuel elements is provided by storing the elements under pond water, typically of 6 to 7 m in depth. Controls are applied to the stacking of fuel skips, this being normally limited to double stacking. Interlocks on the pond cranes and other equipment limit the height to which the fuel skips and individual elements can be raised during transfer and handling, such that an ade­quate depth of water for shielding, i. e., about 3.7 m, is always maintained.

At those stations where the fuel transport flasks are loaded in the pond, there are interlocks to prevent the flask being raised without its lid.

Other precautions include installed instruments such as high and low pond water level alarms, and gamma radiation monitors. Anti-syphon precautions are com­monly included in pond water treatment supply or delivery lines. Strict health physics controls are applied to the removal of items from the ponds.

Internal shielding walls fitted with stop gates enable the various working areas of the pond to be segregated and drained for maintenance work.